1. Technical Field
This invention relates to a filter press electrolyzer electrode assembly. Each electrode of the assembly is of a type having a back pan with electrodes spaced apart from the back pan by stand-offs. The electrolyzer can be used for the electrolysis of an electrolyte to generate a product such as chlorine and caustic soda.
2. Description of the Prior Art
It has been known to electrolyze a bath such as of salt water by using bar electrodes which are equidistantly positioned in parallel at both sides of a separating membrane. Apparatus as depicted in U.S. Pat. No. 4,211,628 has such bar electrodes and the electrodes are rigidly affixed to stiffeners. The bar electrodes can be positioned opposite one another on both sides of the separating membrane, or they can be offset from one another so as to position the membrane between opposing bar electrodes in a zigzag manner. For the offsetting arrangement, this is taught to shorten the inter-electrode distance.
Where the electrode is a mesh, such as a valve metal mesh screen, the membrane may be sandwiched between an anode screen and a cathode screen. In the structure depicted in U.S. Pat. No. 4,343,689, electrical current may be applied to the electrode screens by rigid ribs. It is therein taught in the patent that the ribs for the anode structure should be offset from the ribs of the cathode structure to avoid pinching of the membrane between the ribs, which would cause possible rupture of the membrane. In addition to rigid ribs, the current conducting means might be resilient and, by being offsetting, will provide a resilient sinusoidal bending of the electrode mesh. Even where the ribs are replaced, as by a sheet bent in a corrugated manner, the bends of the sheet are offset as such bends are shown to provide substantially the same, almost point or edge, contact as provided by the ribs.
It has also been taught that the membrane may be fabricated to include matter beyond the basic membrane. The added matter can take the form of porous layers, which have no electrode activity, as has been disclosed in the U.S. Pat. No. 4,617,101. There can be disposed against such an augmented membrane a flexible electrode. Where opposing electrodes are in rod form, a form as has been discussed hereinabove, they may be offset.
In electrode assemblies for membrane cells where the electrolyzer is a filter press electrolyzer, such electrode assemblies can have mesh electrodes which are separated by stand-offs from a back pan. As disclosed in U.S. Pat. Nos. 4,738,763 and 4,923,582, these stand-offs for the electrode assemblies can be spring members. The spring members may include large flat contact areas with the electrodes. Moreover, the spring stand-off members from the anode compartment can oppose directly the spring members from the cathode compartment.
Where the stand-offs have the configuration of a channel member, they may have a large, flat upper member, which can be plate-like, in contact with the mesh electrode. Or, after repair, they may have large, flat upper surfaces in the nature of a mesh structure that are in contact with the mesh electrode. Such structures have been shown for example in U.S. Pat. No. 5,454,925. When the upper flat member is plate-like, it is known that this member can be perforate by providing a single or double line of small holes along the length of the plate. It would be desirable in these structures to provide for a more uniform mechanical and hydraulic pressure against the membrane. It would also be desirable to combine such pressure improvements with enhanced electrode assembly operating efficiencies as well as with reduced wear on the membrane face.